A Review of the Chemical Ecology of Antarctic Marine Invertebrates

The interdisciplinary field of marine invertebrate chemicalecology is relatively young, and particularly so in polar marineenvironments. In this review we present evidence that the incidenceof chemical defense in antarctic benthic marine invertebratephyla is widespread. Mechanisms of chemical defense have beendetected in antarctic representatives of the Porifera, Cnidaria,Brachiopoda, Tunicata, Nemertea, Mollusca and Echinodermata.This argues against earlier bio-geographic theories that predicteda low incidence of chemical defense in polar waters where levelsof fish predation are low. Selection for chemical defense inbenthic sessile and sluggish marine invertebrates is likelya response to an environmentally stable community shown to bestructured primarily by biotic factors such as predation andcompetition. Holoplankton and the eggs, embryos and larvae ofboth benthic and planktonic antarctic macroinvertebrates mayalso employ chemical defense to offset mortality during characteristicallyslow development and long life span where susceptibility topredation is seemingly high. While most research to date hasfocused on the role of secondary metabolites in mediating predation,it is likely that bioactive compounds in antarctic marine invertebratesalso serve roles as antifoulants and allelochemics. The diversityof bioactive metabolites detected to date in antarctic marineinvertebrates sets the stage both for continuing and for broadeningefforts to evaluate their functional and ecological significance.     

Bighorn Sheep Abundance Following a Suspected Pneumonia Epidemic in Rocky Mountain National Park

Abstract: Anecdotal evidence of a pneumonia epizootic among bighorn sheep (Ovis canadensis canadensis) in Rocky Mountain National Park (RMNP), Colorado, USA, during the mid-1990s prompted park officials to examine the current condition of the herds. Here we present a mark—resight study design to estimate population abundance that, in many circumstances, is a reliable and cost-effective alternative to traditional mark—recapture or to indices of population abundance. We captured 59 adult females and radiocollared them via helicopter net-gunning during winter 2002–2003. From ground resighting surveys conducted May—September, we estimated the total RMNP bighorn population at 389.9 (SE = 34.9, CI = 327.2–464.6) in 2003 and 366.4 (SE = 34.7, CI = 304.4–441.0) in 2004. Previous abundance estimates suggest a park-wide decline has occurred between the late 1980s and the suspected pneumonia epidemic of the mid-1990s. Although the 2 years of data from our study are not enough to predict whether the herds are capable of recovering to previous levels, they provide park officials the tools necessary to make the most informed decisions for future monitoring and management of this fragile species.     

Reproduction of Antarctic Benthic Marine Invertebrates: Tempos, Modes, and Timing

Work on the life histories of common antarctic benthic marineinvertebrates over the past several decades demands a revisionof several widely held paradigms. First, contrary to expectationsderived from work on temperate species, there is little or noevidence for temperature adaptation with respect to reproduction(gametogenesis), development, and growth. It remains to be determinedwhether the slow rates of these processes reflect some inherentinability to adapt to low temperatures, or are a response tofeatures of the antarctic marine environment not directly relatedto low temperature, such as low food resources. Secondly, contraryto the widely accepted opinion designated as "Thorson's rule,"pelagic development is common in many groups of shallow-watermarine invertebrates. In fact in some groups, such as asteroids,pelagicdevelopment is as prevalent in McMurdo Sound, the southern-mostopen-water marine environment in the world, as in central California.In other taxonomic groups, especially gastropods, there doesseem to be a genuine trend toward non-pelagic development fromtropical to antarctic latitudes. Although this trend has beenpredicted by theoretical models, its underlying causes appearto be group specific rather than general. Thirdly, pelagic lecithotrophicdevelopment, often considered to be of negligible importance,occurs in many shallow-water antarctic marine macroinvertebrates.Pelagic lecithotrophy may be an adaptation to a combinationof poor food conditions in antarctic waters most of the yearand slow rates of development. Nevertheless, some of the mostabundant and widespread antarctic marine invertebrates havepelagic planktotrophic larvae that take very long times to completedevelopment to metamorphosis. These species areparticularlyprevalent in productive regions of shallow water (<30 m),which are frequently disturbed by anchor ice formation, andthe production of numerous pelagic planktotrophic larvaemayrepresent a strategy for colonization. Although planktotrophiclarvae tend to be seasonal in occurrence, their production isnot linked particularly closely to the mid-summer pulse of phytoplanktonproduction. These larvae show no evidence of starvation, evenduring times when phytoplankton abundance is very low, and theymay depend on unusual sources of food, such as bacteria. Howthey escape the selective conditions that apparently led toa predominance of non-feeding modes of development in antarcticmarine invertebrates remains as a major challenge for antarcticmarine biology.     

Mark-Resight Methodology for Estimating Population Densities for Prairie Dogs

Abstract: Accurate assessments of local population size of the black-tailed prairie dog (Cynomys ludovicianus) are essential because of their overall decline and importance to prairie ecosystems. We describe the use of mark-resight methodology to estimate black-tailed prairie dog population size and density. Study colonies include isolated urban habitat fragments in Denver, Colorado, USA, and unfragmented control colonies in the Pawnee National Grassland, USA. We compare results from various mark-resight estimators to those derived from linear transformations of visual counts of active prairie dogs. Our results suggest that mark-resight methods are feasible in both urban and rural systems, and reveal extremely high densities for isolated prairie dogs in urban sites. Our methodology can be used to obtain reliable, unbiased estimates of local population size and density.     

Social Control of the Ovarian Cycle and the Function of Estrous Synchrony

SYNOPSIS. The social signals among groups of females can eitherenhance or suppress ovariancyclicity. The ovarian cycle is notunitary, but is instead the integrated product of several differentcomponents which are each affected by social signals of differentmodalities. This interaction between female behavior and ovariancycle components has different manifestations in different species.Depending on its temporal context and the social and physicalenvironment, the same behavior/hormone interaction can takedifferent forms. In some contexts, these interactions can beadaptive for the individual. In others, they can generate astrong epiphenomenon or artifact that may not confer a directadaptive advantage itself, but still be necessary for otheraspects of the coordination between social behavior and reproduction.